Terminals come in a wide variety of configurations for different environments. Telecommunications terminals were optimized for use with copper drop wires. Through an evolutionary process, a plurality of different wire sizes and kinds of wire are employed to connect the subscriber to the phone company. The gauges can vary from 12-30 AWG gauge copper based wires some of which may have steel cores. Most common wire sizes are between 16-26 gauge. Standard conventional terminals have a threaded binding post embedded in a suitable dielectric base material. The drop wire is stripped of its insulation, formed in a "C" shape, and connected to the terminal post by nuts and washers. This procedure is craft sensitive and time consuming. These terminals, while extremely low cost, suffer high maintenance and repair costs due to corrosion, e.g., oxidation on the exposed wires and binding posts. In addition, wet/humid weather, or periodic water submersion, or salt/fog corrosion, or dew on insect nests can cause cross talk or signal loss. A serviceman is dispatched in response to a customer complaint only to find that the problem has disappeared due to the evaporation of the moisture.
Insulation displacement terminals, which cut through the wire insulation without requiring wire stripping, address the time consuming installation problems. However, many of these terminals also suffer from corrosion, often more severe than standard binding post and washer/nut terminals. In addition, overnotching of the conductor may sever or severely weaken the drop wire rendering it subject to premature failure. The premature failure of the drop wires significantly increases the telephone company's repair costs. In addition, initial use of the terminal on a large drop wire may damage the terminal and preclude its subsequent use on smaller drop wires.
U.S. application Ser. Nos. 07/462,173, filed Jan. 8, 1990, now U.S. Pat. No. 5,069,636, 07/231,755 filed Aug. 13, 1988, now abandoned, and U.S. Pat. No. 4,846,721 solved many of these problems with a uniquely formed electrical connection and sealing system utilizing a reenterable gel material. The gel sealing system utilized in the terminals are, inter alia, disclosed in U.S. Pat. Nos. 4,865,905; 4,864,725; 4,600,261; 4,634,207; 4,643,924; and 4,690,831. However, these blocks were only readily adaptable to wires, e.g., drop wires. These preceding specifications and patents are completely incorporated herein by reference for all purposes.
Although these terminals can form electrical contacts to a plurality of different wire sizes, an even easier, more versatile system would be desirable. In addition, with an increasing use of computers, and the overcrowding of conventional telephone lines limiting the capacity of the copper plant system architecture, a terminal which can be subsequently adapted after installation, to include circuit protection, filters, cable TV, optical fibers, and/or digitizing of the telephone signal, e.g., digital added main lines, (DAML), to increase the number of different phone numbers available through each twisted pair of wires, would be highly desirable.
It would also be desirable to have a modular drop wire unit which is simple for the craftsperson to install and keyed to the block to avoid misinsertions. It would additionally be desirable to have a unit which can adequately seal in a reversible fashion between the drop wire module and the block itself for subsequent additions to the block such as circuit protection, and the like.
The inability to provide a secure weatherproof system, less subject to outside plant failures, has forced the use of many add-on features, such as fused circuit protection and DAML, at the customer's protected base location. This renders them subject to tampering. The weatherproof system could be centrally located underground, on a telephone pole, or in a centrally located outside enclosure, e.g., a pedestal enclosure. As the system is upgraded, the new features can be plugged into the terminal through the common plug connection.
By a weatherproof system, we mean a modular system that meets the requirements of a present day standard outside nut and washer or insulation displacement terminal that can operate for prolonged periods in the outside plant environment. The block of the invention alone without connections or a block in combination with modules is capable of exhibiting resistance to the elements even after repeated connections/disconnections during its lifetime. At least five connections/disconnections and most likely ten or more can be expected during a terminal's lifetime. Suitable tests are ISO 846 (ASTM G-21) (1985) for fungi and bacteria. The dielectric strength of the electrical insulation in the block must be capable of passing IEC 243 (ASTM D-149) (1981). The block must also must be able to withstand corrosive effects of materials and the effects of liquid chemicals meeting the requirements of ASTM D-2671 (1985) and ISO 175 (ASTM D-543) (1987). While in use, the contact resistance cannot vary greater than the parameters permitted by ASTM B 539-80 (1985 revised) as well as withstanding salt fog testing according to ASTM B-117 (1985). Finally, to be effective the block must be able to operate while exposed to sunlight and water while remaining able to meet the standards of ASTM G-53-84 (1988) and ASTM D-257 (1983).
Thus, it would be highly desirable to have a weatherproof modular system capable of providing repeated reentry of the plug for the drop wire, fuse. digitally added mainline (DAML) apparatus, and the like, without subjecting the terminal to either corrosion or electrical failure.
The process of making the terminals is labor intensive and time consuming. The process requires the individual termination of the copper wires within the cable to the back of the terminal and thereafter potting. An embodiment of the present invention provides for the cable wires to be attached to the terminal posts without precutting. In the prior art, if the wires are cut to an improper length either a splice or a total rewiring of the terminal block was usually required. To provide a lower cost terminal and a more reliable and less labor intensive manufacturing process, it would be highly desirable to have a block which can be tested during the wiring process and prior to wire cutting and assembly.